The present invention relates to a photosensitive composition capable of pattern formation for use in the production of electronic elements such as semiconductor devices and liquid crystal display devices.
For production of electronic device such as semiconductor elements, integrated circuits, fine processing techniques by photoetching is used. For photoetching, for example, a resist film is formed on a silicon monocrystal wafer etc. by spin coating and exposed to light via a mask having a desired pattern. Then, the resist film after exposure to light is subjected to development treatment and then rinsed to form a resist pattern. Thereafter, the resulting pattern is used as an etching mask to etch the wafer to form a line or open a window.
In the fine processing techniques, product accuracy depends mainly on the performance of the resist used, i.e. resolution on a substrate, accuracy of photosensitivity, and adhesive properties on the substrate or resistance to etching.
Recently, there is increasing hope of polysilane as such a resist. For examples, the techniques of forming a positive pattern by use of polysilane are disclosed in Jpn. Pat. Appln. KOKAI Publication No. 62-228542. A pattern formed using a resist containing a silicon-containing compound such as polysilane has the following characteristics: If such a resist pattern is subjected to oxygen reactive ion etching (oxygen RIE), a film made of e.g. SiO.sub.2 is formed on the surface of the resist film. Accordingly, the resist pattern has high oxygen RIE properties.
In this prior art, however, a volatile photo-depolymerization polymer is formed by irradiating polysilane with actinic radiation, and then the formed photodepolymerization polymer is evaporated to form a pattern. Therefore, it is very difficult to form a fine pattern accurately in such dry development. Further, there is also the problem that the formation of a pattern by means of conventional polysilane is still inadequate in respect of sensitivity.
As an alternative method, a method of forming a pattern by use of polysilane in wet etching is proposed. Polysilane possesses the properties by which its molecular weight is reduced upon exposure to light by irradiation with ultraviolet light. Therefore, a polysilane film formed on a substrate is selectively exposed to light and then developed by selectively dissolving it in a polar solvent such as alcohol, ketone etc. to form a pattern.
However, when pattern formation is carried out by use of a photosensitive composition consisting of polysilane only, several joules/cm.sup.2 are required as exposed light. In addition, there is the problem that the sectional shape and resolution of the resulting pattern become poor.
Although pattern formation by use of polysilane as a resist has been attempted as described above, it is often difficult to form a fine pattern accurately and sensitivity is also often poor in the case of a resist containing only polysilane. Further, if pattern formation is made feasible by alkali development, an improvement in pattern accuracy can be expected, but polysilane is generally insoluble in an aqueous alkaline solution, so pattern formation by alkali development is not possible.
In view of the above-described problems an object of the invention is to provide a photosensitive composition capable of accurately and highly sensitively forming a fine pattern excellent in sectional shape.
Another object of the present invention is to provide a pattern forming method capable of forming a fine pattern by alkali development.
A further object of the present invention is to provide a process for producing an electronic device, which comprises using the resulting pattern to carry out fine processing accurately.